HIM keeps a list of the units of measurements that can be used as the value of the `unit`

metadata, see the example below.

```
Vehicle.Speed:
datatype: float
type: sensor
unit: km/h
description: Vehicle speed.
```

Data that has an associated unit from the list shall declare it using the `unit`

metadata.
It is allowed for a domain to specify an additional list with domain specific units that complement the common units list.
Units shall if possible be based on SI-units, but exceptions like the speed example above are acceptable.
The list contains entries of a unit with a prefix, e. g. `mm`

for millimeter, which are the only prefixes that are valid.
The unit must be written exactly as shown in the list.

In some cases it is natural to omit the data unit type. This concerns typically signals where data type `string`

is used,
but also signals where the value just represents a number, like in the example below:

```
Vehicle.Cabin.DoorCount:
datatype: uint8
type: attribute
default: 4
description: Number of doors in vehicle.
```

HIM also supports `percent`

and `ratio`

as data units.

This list is mainly derived from the International System of Units (SI).

Unit | Domain | Description |
---|---|---|

mm | Distance | Distance measured in millimeters |

cm | Distance | Distance measured in centimeters |

m | Distance | Distance measured in meters |

km | Distance | Distance measured in kilometers |

inch | Distance | Distance measured in inches |

km/h | Speed | Speed measured in kilometers per hours |

m/s | Speed | Speed measured in meters per second |

m/s^2 | Acceleration | Acceleration measured in meters per second squared |

cm/s^2 | Acceleration | Acceleration measured in centimeters per second squared |

ml | Volume | Volume measured in milliliters |

l | Volume | Volume measured in liters |

cm^3 | Volume | Volume measured in cubic centimeters |

celsius | Temperature | Temperature measured in degree celsius |

degrees | Angle | Angle measured in degrees |

degrees/s | Angular Speed | Angular speed measured in degrees per second |

W | Power | Power measured in watts |

kW | Power | Power measured in kilowatts |

PS | Power | Power measured in horsepower |

kWh | Energy Consumption | Energy consumption measured in kilowatt hours |

g | Weight | Mass measured in grams |

kg | Weight | Mass measured in kilograms |

lbs | Weight | Mass measured in pounds |

V | Electric Potential | Electric potential measured in volts |

A | Electric Current | Electric current measured in amperes |

Ah | Electric Charge | Electric charge measured in ampere hours |

ms | Time | Time measured in milliseconds |

s | Time | Time measured in seconds |

min | Time | Time measured in minutes |

h | Time | Time measured in hours |

day | Time | Time measured in days |

weeks | Time | Time measured in weeks |

months | Time | Time measured in months |

years | Time | Time measured in years |

UNIX Timestamp | Time | Unix time is a system for describing a point in time. It is the number of seconds that have elapsed since the Unix epoch, excluding leap seconds. |

mbar | Pressure | Pressure measured in millibars |

Pa | Pressure | Pressure measured in pascal |

kPa | Pressure | Pressure measured in kilopascal |

stars | Rating | Rating measured in stars |

g/s | Mass per time | Mass per time measured in grams per second |

g/km | Mass per distance | Mass per distance measured in grams per kilometers |

kWh/100km | Energy Consumption per distance | Energy consumption per distance measured in kilowatt hours per 100 kilometers |

ml/100km | Volume per distance | Volume per distance measured in milliliters per 100 kilometers |

l/100km | Volume per distance | Volume per distance measured in liters per 100 kilometers |

l/h | Flow | Flow measured in liters per hour |

mpg | Distance per Volume | Distance per volume measured in miles per gallon |

N | Force | Force measured in newton |

Nm | Torque | Torque measured in newton meters |

rpm | Rotational Speed | Rotational speed measured in revolutions per minute |

Hz | Frequency | Frequency measured in hertz |

ratio | Relation | Relation measured as ratio |

percent | Relation | Relation measured in percent |

… | … | … |